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Biomedical subjects

A Cerami

Publications and source records attributed to A Cerami.

At least 199 records · Page 11Linked to original sources
PubMed1987

In vivo effects of difluoromethylornithine on trypanothione and polyamine levels in bloodstream forms of Trypanosoma brucei.

The effect of D,L-alpha-difluoromethylornithine (DFMO) on thiol and polyamine levels in Trypanosoma brucei was investigated by isolating trypanosomes from infected rats treated with DFMO for 12-48 h. Concentrations of thiols, polyamines and other amino-compounds were measured by an automated high-performance liquid chromatography method. The levels of DFMO in rat plasma (0.02-1.34 mM) is similar to that found in the parasites (0.27-0.99 mM), concentrations which exceed the Ki of DFMO for T. brucei ornithine decarboxylase. Treatment with DFMO increases intracellular levels of ornithine, S-adenosylmethionine and decarboxylated S-adenosylmethionine and decreases putrescine and spermidine. Putrescine is undetectable after 12 h treatment with DFMO and after 48 h spermidine is decreased by 76%. By 48 h, the spermidine-glutathione conjugates glutathionylspermidine and dihydrotrypanothione (bis(glutathionyl)spermidine) are also decreased by 41 and 66%, respectively. In contrast, levels of glutathione show a slight increase. These changes in metabolite levels are consistent with the biosynthetic pathway proposed for Crithidia fasciculata, where trypanothione is synthesized from spermidine and glutathione via the intermediates N1- and N8-glutathionyl-spermidine. Trypanothione is thought to have two important roles in trypanosomatid metabolism: the maintenance of intracellular thiols in the correct redox state and in the removal of hydrogen peroxide and other hydroperoxides. Thus, it is proposed that depletion of this metabolite may be an important contributory factor to the selective toxic effect of DFMO, particularly in its synergistic effect with other trypanocidal drugs.

Animals↗
PubMed1987

Trypanothione dependent peroxide metabolism in Crithidia fasciculata and Trypanosoma brucei.

A trypanothione-dependent peroxidase activity has been identified in the insect trypanosomatid Crithidia fasciculata and in the mammalian trypanosome Trypanosoma brucei. Using organic hydroperoxides as oxidant, specific peroxidase activities in these organisms are 5.0 and 1.0 nmol min-1 (10(8) cells)-1 respectively. The T. brucei peroxidase had an activity of 0.4 nmol min-1 (10(8) cells)-1 using hydrogen peroxide as oxidant. The enzyme is specific for the N1,N8-bis(glutathionyl)spermidine conjugate (dihydro-trypanothione); N1-mono-glutathionylspermidine is not a substrate. Experiments to demonstrate that this parasite peroxidase may contain selenium were inconclusive. However, bloodstream T. brucei can incorporate radiolabelled selenite into proteins.

Animals↗
PubMed1987

Cachectin--Tumour necrosis factor: a cytokine that mediates injury initiated by invasive parasites.

The primary role for which the immune system evolved was a protective one, yet there is no doubt that immune mechanisms can also injure the host. Frequently cited examples of immune-mediated injury include complement-induced disease processes, diseases caused by immune complexes, or those that result from cell-mediated hypersensitivity. During the past few years however, it has become clear that the immune system can also express itself through the action of various cytokines. Gradually, it has been appreciated that these agents may cause disease when produced excessively or inappropriately, and in this article Bruce Beuder and Anthony Cerami discuss one of the most important of these cytokines - cochectin or tumour necrosis factor (TNF).

Journal Article↗
PubMed1987

Hookworm antigens: the potential for vaccination.

Hookworms rank with Ascaris as the most prevalent soil-transmitted helminths of man. Up to 1000 million people may be infected. Not all suffer the life-threatening anaemia that reflects heavy burdens of hookworms, but even mild iron-deficiency anaemia due to hookworms can lead to intellectual and growth retardation - especially among infected children. Health education, mass chemotherapy and the sanitary disposal of faeces have been the traditional mainstays of hookworm control, but more recently chemotherapy targeted only to heavily infected individuals who appear predisposed to hookworm anaemia has emerged as a realistic alternative. Ultimately, however, knowledge of the molecular immunology of hookworm infection may provide the basis for rational vaccine development. Although the evidence for acquired immunity to hookworms in man is not strong, work is now underway to identify and to characterize antigens from third and fourth larval stages and adults of Necator americanus and species of Ancylostoma (Table 1). As this article shows, the work provides real promise for improved immunodiagnosis and possible vaccination.

Journal Article↗
PubMed1987

Elevated glucose 6-phosphate levels are associated with plasmid mutations in vivo.

The incubation in vitro of plasmid pBR322 DNA with glucose 6-phosphate (Glc-6-P) has been shown to have a mutagenic effect when the plasmid was transformed into wild-type Escherichia coli. To further investigate the modifications of DNA by the reducing sugar Glc-6-P, we have developed an in vivo model to monitor plasmid DNA mutations. E. coli strains that are defective for phosphoglucose isomerase (strain DF40) alone or phosphoglucose isomerase and glucose-6-phosphate dehydrogenase (strain DF2000) accumulate Glc-6-P when grown in gluconate minimal medium in the presence of glucose. These strains and the control strain K10 were transformed with pAM006, a plasmid that carries the genes for ampicillin resistance and beta-galactosidase production, and grown for 24 hr under conditions that prompted the accumulation of Glc-6-P. An increase in plasmid mutations was observed (7- and 13-fold) that was associated with the increased intracellular levels of Glc-6-P (20- and 30-fold) present in the DF40 and DF2000 E. coli strains, respectively. Growth of the mutant bacteria in gluconate minimal medium does not increase the intracellular levels of Glc-6-P or the rate of plasmid mutations over background. Further characterization of the mutated plasmid DNA showed that insertions, deletions, and point mutations were responsible for the loss of beta-galactosidase production. The increase in plasmid mutations as a function of increased intracellular Glc-6-P levels suggests that the accumulation of adducts formed by Glc-6-P and other reducing sugars may contribute to DNA damage.

DNA Restriction Enzymes↗
PubMed1987

Effect of endotoxin-induced monokines on glucose metabolism in the muscle cell line L6.

Exposure of fully differentiated L6 myotubes to a crude monokine preparation from endotoxin-stimulated RAW 264.7 cells resulted in a rapid and substantial (70%) increase in fructose 2,6-bisphosphate concentration coincident with a depletion of cellular glycogen and an increased lactate production. During the time required for glycogen depletion (3 hr), stimulation of 3-O-methyl-D-glucose and 2-deoxy-D-glucose uptake was initiated and observed to reach a maximum enhancement of 200% 12-15 hr later. The monokine had no effect on the Km value for 2-deoxy-D-glucose uptake (1.1 mM), while Vmax was increased from 912 to 2400 pmol/min per mg of protein. The increase was cytochalasin B inhibitable and was dependent on protein synthesis. Photoaffinity labeling and equilibrium binding studies with [3H]cytochalasin B support the hypothesis that this increase in hexose transport was due to an increase in hexose transporters present in the plasma membrane. Purified recombinant interleukin-1 alpha had no effect on hexose transport, whereas purified recombinant cachetin/tumor necrosis factor did stimulate hexose uptake, with half-maximal stimulation occurring at 36 nM. Although cachetin accounts for most of the biological activity associated with the crude monokine preparations, it is not the only monokine capable of inducing glucose transport in L6 cells. Specific immunoabsorption of cachectin/tumor necrosis factor from the crude monokine preparation revealed a monokine that had a similar bioactivity at extremely low concentrations on L6 cells.

3-O-Methylglucose↗
PubMed1987

Chemotherapy of trypanosomiasis: the use of guanylhydrazone compounds in the treatment of experimental murine trypanosomiasis.

The efficacy of 1,3,5-triacetylbenzene tris(guanylhydrazone) trihydrochloride i.e. [(TBG)] in the treatment of early and late stage infections of Trypanosoma brucei in mice was investigated. Successful treatment on day 3 after infection could be achieved by doses of 2 X 2.5 mg kg-1. If treatment was delayed to 21 days after infection then the mice had to be given either suramin (1 X 20 mg kg-1) or difluoromethyl-ornithine (DFMO) 2% solution for 14 days in addition to either 15 mg kg-1 (TBG) daily for 4 days or 10 mg kg-1 twice daily for 4 days to obtain permanent cures. Other guanylhydrazone compounds were investigated for the treatment of chronic T. brucei infections and, at the limited dose levels used, failed to give any permanent cures. The use of (TBG) in the treatment of early and late stage infections of T. congolense and T. evansi indicated that treatment on day 3 after infection could be successful but on day 21 after infection the results were disappointing.

Animals↗
PubMed1987

Inhibition of erythroid differentiation of mouse erythroleukemia cells by a macrophage product(s).

Conditioned media from established murine macrophage cell lines (RAW264.7, P388D1, and WEHI-3) incubated with endotoxin in a serum-free medium contain an erythroid inhibitory activity (EIA) that inhibited dimethylsulfoxide-induced erythroid differentiation of mouse Friend virus-transformed erythroleukemia cells. Endotoxin itself has no EIA activity. Partial purification of EIA demonstrated that it is distinct from other macrophage products such as IL-1, TGF beta, ECGF, FGF, G-CSF, hepatocyte stimulating factor, interferon, PDGF, and cachectin/TNF. These findings indicate that EIA is a macrophage product distinct from other monokines.

Animals↗
PubMed1987

Anti-oestrogen antibodies in users of oral contraceptives and in patients with systemic lupus erythematosus.

Recent studies have demonstrated that many patients with SLE have elevated plasma levels of the minor oestrogen metabolite 16 alpha-hydroxyestrone (16 alpha OHE). This oestrogen is unique in its ability to react with lysine residues and form stable, covalent Heyns products with proteins. Increased levels of 16 alpha OHE-modified proteins have been found to occur on the membranes of red cells and lymphocytes in patients with SLE. In the present study, patient and control sera were analysed for the presence of circulating immunoglobulins which react with an oestrogen hapten. Anti-oestrogen antibodies were detected in 26% (9/34) of male and female SLE patients, and were found to correlate both with levels of plasma 16 alpha OHE (P less than 0.001) and with the presence of active disease (P less than 0.005). Surprisingly, this antibody activity was also observed in 25% (13/52) of normal, disease-free women who had a history of oral contraceptive use. No detectable activity was observed in normal men, women who had not taken oral contraceptives, or patients with a variety of other immunological diseases. The possible role of anti-oestrogen antibodies in both the hormonal exacerbation of SLE and in the long-term sequelae of oral contraceptive usage is discussed.

Adult↗
PubMed1986

Effect of gamma interferon on cachectin expression by mononuclear phagocytes. Reversal of the lpsd (endotoxin resistance) phenotype.

IFN-gamma permits the endotoxin-induced production of cachectin by C3H/HeJ (endotoxin resistant) macrophages, apparently by facilitating endotoxin-induced cachectin biosynthesis at both transcriptional and posttranscriptional levels. IFN-gamma cannot induce cachectin biosynthesis by itself, nor does it markedly enhance cachectin production by endotoxin-induced peritoneal macrophages obtained from endotoxin-responsive mice. Elucidation of the precise mechanism through which IFN-gamma influences cachectin biosynthesis may permit a better understanding of the molecular events that follow endotoxin-induced activation of macrophages. Moreover, the permissive effect of IFN-gamma on cachectin biosynthesis might elicit enhanced endotoxin sensitivity in vivo.

Animals↗
PubMed1986

Novel macrophage receptor for glucose-modified proteins is distinct from previously described scavenger receptors.

A high-affinity macrophage receptor has been identified that recognizes proteins modified by a common in vivo process, long-term nonenzymatic reaction of glucose with proteins (AGE proteins). This receptor for glucose-modified proteins is now shown to be distinct from previously described scavenger receptors, using competition and crosscompetition experiments between AGE-modified protein and a variety of in vitro-modified scavenger receptor ligands, including unmodified BSA, unmodified low-density lipoproteins (LDL), acetyl-LDL, maleyl-BSA, and formaldehyde-treated BSA. Furthermore, the specific pattern of AGE-protein receptor inhibition by the polyanionic compounds polyinosinic acid, polyadenylic acid, polyglutamic acid, polycytidylic acid, fucoidin, and heparin was distinctly different from that of acetyl-LDL. By thus selectively recognizing a time-dependent in vivo protein modification, macrophages may preferentially degrade senescent macromolecules, thereby having an important role in the regulation of extracellular protein turnover.

Aging↗
PubMed1986

Cachectin/tumor necrosis factor mediates changes of skeletal muscle plasma membrane potential.

Lethal infections are associated with cellular dysfunction as evidenced by a decrease in the resting transmembrane potential difference (Em) of skeletal muscle fibers. Endotoxin stimulation of macrophages evokes production of cachectin, a protein that has been implicated as a mediator of the lethal effects of endotoxemia. In the present study, rat skeletal muscle fiber Em decreased when incubated with recombinant human cachectin. The reduction of Em induced by cachectin occurred in a dose-related fashion and was inhibited by mAb against the monokine. Infusion of cachectin induced a decline of skeletal muscle Em in vivo, and suggests that cachectin may acutely mediate alterations of skeletal muscle membrane function after infection.

Animals↗
PubMed1986

Aminoguanidine prevents diabetes-induced arterial wall protein cross-linking.

Age-associated increases in collagen cross-linking and accumulation of advanced glycosylation products are both accelerated by diabetes, suggesting that glucose-derived cross-link formation may contribute to the development of chronic diabetic complications as well as certain physical changes of aging. Aminoguanidine, a nucleophilic hydrazine compound, prevented both the formation of fluorescent advanced nonenzymatic glycosylation products and the formation of glucose-derived collagen cross-links in vitro. Aminoguanidine administration to rats was equally effective in preventing diabetes-induced formation of fluorescent advanced nonenzymatic glycosylation products and cross-linking of arterial wall connective tissue protein in vivo. The identification of aminoguanidine as an inhibitor of advanced nonenzymatic glycosylation product formation now makes possible precise experimental definition of the pathogenetic significance of this process and suggests a potential clinical role for aminoguanidine in the future treatment of chronic diabetic complications.

Animals↗
PubMed1986

Purification and characterization of trypanothione reductase from Crithidia fasciculata, a newly discovered member of the family of disulfide-containing flavoprotein reductases.

Trypanothione reductase from Crithidia fasciculata has been purified ca. 1400-fold to homogeneity in an overall yield of 60%. The pure enzyme showed a pH optimum of 7.5-8.0 and was highly specific for its physiological substrates NADPH and trypanothione that had Km values of 7 and 53 microM, respectively. Trypanothione reductase was found to be a dimer of identical subunits with Mr 53 800 each. The enzyme displayed a visible absorption spectrum that was indicative of a flavoprotein with a lambda max at 464 nm. The flavin was liberated by thermal denaturation of the protein and identified, both by high-performance liquid chromatography (HPLC) and by fluorescence studies, as FAD. The extinction coefficient of pure enzyme at 464 nm was determined to be 11.3 mM-1 cm-1. Upon titration with 5,5'-dithiobis(2-nitrobenzoic acid), oxidized enzyme was found to contain 2.2 (+/- 0.1) free thiols, whereas NADPH-reduced enzyme showed 3.9 (+/- 0.3). Furthermore, whereas oxidized enzyme was stable toward inactivating alkylation by 2.0 mM iodoacetamide, NADPH-reduced enzyme was inactivated with a half-life of 14 min. These data suggested that a redox-active cystine residue was present at the enzyme active site. Upon reduction of the enzyme with 2 electron equiv of dithionite, a new peak in the absorption spectrum was observed at 530 nm, thus indicating that a charge-transfer complex between one of the newly reduced thiols and the oxidized FAD had formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1986

Tumor necrosis factor (cachectin) is an endogenous pyrogen and induces production of interleukin 1.

Recombinant human tumor necrosis factor (rTNF alpha) injected intravenously into rabbits produces a rapid-onset, monophasic fever indistinguishable from the fever produced by rIL-1. On a weight basis (1 microgram/kg) rTNF alpha and rIL-1 produce the same amount of fever and induce comparable levels of PGE2 in rabbit hypothalamic cells in vitro; like IL-1, TNF fever is blocked by drugs that inhibit cyclooxygenase. At higher doses (10 micrograms/kg) rTNF alpha produces biphasic fevers. The first fever reaches peak elevation 45-55 min after bolus injection and likely represents a direct action on the thermoregulatory center. During the second fever peak (3 h later), a circulating endogenous pyrogen can be shown present using passive transfer of plasma into fresh rabbits. This likely represents the in vivo induction of IL-1. In vitro, rTNF alpha induces the release of IL-1 activity from human mononuclear cells with maximal production observed at 50-100 ng/ml of rTNF alpha. In addition, rTNF alpha and rIFN-gamma have a synergistic effect on IL-1 production. The biological activity of rTNF alpha could be distinguished from IL-1 in three ways: the monophasic pyrogenic activity of rIL-1 was destroyed at 70 degrees C, whereas rTNF alpha remained active; anti-IL-1 neutralized IL-1 but did recognize rTNF alpha or natural cachectin nor neutralize its cytotoxic effect; and unlike IL-1, rTNF alpha was not active in the mitogen-stimulated T cell proliferation assay. The possibility that endotoxin was responsible for rTNF alpha fever and/or the induction of IL-1 was ruled-out in several studies: rTNF alpha produced fever in the endotoxin-resistant C3H/HeJ mice; the IL-1-inducing property of rTNF alpha was destroyed either by heat (70 degrees C) or trypsinization, and was unaffected by polymyxin B; pyrogenic tolerance to daily injections of rTNF alpha did not occur; levels of endotoxin, as determined in the Limulus amebocyte lysate, were below the minimum rabbit pyrogen dose; and these levels of endotoxin were confirmed by gas chromatography/mass spectrometry analysis for the presence of beta-hydroxymyristic acid. Although rTNF alpha is not active in T cell proliferation assays, it may mimic IL-1 in a T cell assay, since high concentrations of rTNF alpha induced IL-1 from epithelial or macrophagic cells in the thymocyte preparations. These studies show that TNF (cachectin) is another endogenous pyrogen which, like IL-1 and IFN-alpha, directly stimulate hypothalamic PGE2 synthesis. In addition, rTNF alpha is an endogenous inducer of IL-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗